Transfer circuits for electric signals



Oct. 11, 1960 Filed May 26, 1954 J B W F w 1 M14 62 8 m L Mk C. .II 9 5k w? Z. a M Q 6 WW W 9 ,3 1M ,1 A 7 J2 0 (O/VIM T BE H1765 l I l FTTTT7P7 ATTOR United States Patent TRANSFER CIRCUITS FOR uzmmc SIGNALS JacquesAlbin, Le Vesinet, France, assignor to Societe dElectronique etdAutomatisme, Courbevoie, France Filed May 26, 1954, Ser. No. 432,455

Claims priority, application France June 3, 1953 19 Claims. (Cl. 340174)The present invention relates to improved transfer circuits for electricsignals having a two-level voltage waveform and being similar in thisrespect to conventional coded signals for telegraphic purposes and thelike.

More specifically, it relates to improved transfer circuits for electricsignals of such a rectangular waveform which are adapted to be stored byregistration upon a magnetic recording medium such as a magnetic drum orthe like.

' The general object of the invention is in the provision of a transfercircuit without vacuum tubes which is economical and simple but of longlife and stability of operation.

Another object of the invention is the provision of such a transfercircuit which can be used, in combination with a plurality of identicaltransfer circuits, for the constitution of a transfer arrangementcapable under control of selection signals of routing towards separateutilisation or load channels therefor, any electrical signals of theabove-defined shape which are applied to such an arrangement through asingle input transmission channel.

A further object of the invention therefore is in the provision of sucha routing device wherein any and all incoming signals are applied to theinputs of all and any of a plurality of elementary transfer circuits andwherein each of said elementary transfer circuits may or may not beselectively activated from said signals, under the control of selectionsignals, for accordingly routing these incoming signals to at least oneutilisation or load channel among a corresponding plurality of suchchannels each of which is connected to the output of one of theseelementary transfer circuits.

According to the invention, an elementary transfer circuit for theherein above defined purposes includes a pair of magnetic cores ortoroids of quasi-rectangular hysteresis cycles, at least one activationwinding, a selection control winding and an output pick-up winding oneach of said cores, an output load in series between the output pick-upwindings, a series connection for the two selection control windings andmeans for applying thereto a selection control voltage, means forapplying to one of these activation windings in said pair of cores andconcomit'antly therewith the complementary two-level waveform of saidincoming electric signal.

According to the invention further, a selective routing transfer deviceincludes a plurality of such elementary transfer circuits, wherein said"means for applying any incoming electric signal to one of theactivation windings of a pair of cores in an elementary transfer circuitare common to all the elementary transfer circuits in said plurality, aswell as are common to said elementary transfer cirouits of saidplurality for also applying concomitant electric signals of a wave-formcomplementary to said incoming signals, and wherein said means for theapplication to these pairs of series connected selection controlwindings of said elementary transfer circuits are separately providedfor any andall elementary transfer circuits of said plurality.

These and other features will become apparent from the following, whenconsidering the attached drawings, wherein:

Fig. 1 shows a routing transfer arrangement including three elementarytransfer circuits;

Fig. 2 shows signal graphs explaining the operation of the device ofFig. 1; and,

Fig. 3 shows the hysteresis cycles of a pair of magnetic cores of anelementary transfer device of Fig. 1.

Each of the three elementary transfer circuits I, II and III of Fig. 1includes the two identical magnetic cores 1 and 2. The magnetic materialof these cores is such that its hysteresis cycle is substantiallyrectangular as indicated in Fig. 3.

The magnetic core 1 is provided with an activation or energizationwinding 3, a selection control winding 5 and an output pick up winding7. The magnetic core 2 is similarly provided with an activation winding4, a selection control winding 6 and a pick-up winding 8. These coresand windings are identical by pairs and, for the complete arrangementwhich may include as many elementary transfer circuits as desired, theyare selected to be identical through this complete arrangement.

A load impedance 9 is connected between the two pick-up windings 7 and 8of each elementary circuit. One end of each of these windings, the samefor all with respect to their direction of winding upon the magneticcore, is placed at a predetermined potential, viz. the ground potentialfor instance. In each elementary transfer circuit, consequently, theload impedance 9 is connected in series between the ends of twooppositely wound windings. In this arrangement, the other ends of thesewindings have the same potential.

The load impedances 9 may consist, as stated before, of magneticrecording heads for the registration of signals upon a magnetic medium,for instance upon separate tracks of a magnetic drum. The electricsignals under consideration will relate to such a use of the devicereferred to herein.

The windings 3 of all the cores 1 of the elementary cir cuits areserial-1y connected in additive relation and similarly interconnectedare the windings 4. The windings 3 will receive the electric signalsappearing at a common input 10. concomitantly, the windings 4- willreceive, with same timing and phase, the complementary waveform signalswhich will appear at the common input 11. These inputs for instance aretaken from the plates of vacuum tubes, not shown, and the free ends ofthe series connections between windings 3, on one hand, and windings 4,on the other hand, will then be connected to the high voltage suppliesfor the plates of such signal current sources.

An illustrative example of the waveforms of the signals appearing at theinput terminals 10 and 11 is given in the graphs of Fig. 2, whereinthese signals are denoted by I and 1,. Their waveforms, of a totalduration T, are obviously complementary (or of opposite polarity withrespect to each other). They are constituted by rectangular variationsof current between the 0 level (no current) and an I level (arbitraryvalue of maximum current). It is apparent that, during a time intervalT, each time the current I is at its high value l the current T presentsits minimum value 0, and conversely. This is what is meant bycomplementary currents. Furthermore, the waveforms shown are of a kindwell-known for magnetic recording. The two conditions 0 and I can onlysubsist alternatively for the one or the other of two time intervals,here denoted by 0/2 and 0. Such a restriction is not imperative per seand the ratios between the time intervals of the higher and lower valuesof current may be taken different, and even not uniform, during theexistence of any signal. A condition of duration does exist,

however, resulting from technological considerations of the kind ofmagnetic material used for the cores: said minimum value must be such asto permit a change of m'agnetisation within said material, viz. adisplacement of the magnetic induction point upon the hysteresis cycleshown in Fig. 3, for any concerned magnetic core.

For the selective control of the circuits of Fig. l, the windings 5 and6 of each pair are serially connected in each circuit. A current of thevalue I Fig. 2, must be applied to a pair of windings 5-6 for makingthis selection and thus controlling the transfer through thecorresponding pair of magnetic cores, of the electric signal incoming at10-11 to the output load 9 of this pair. Each series circuit 5-6 isconnected at one end to an input terminal 13. Said terminal may be theoutput point of the plate of a vacuum tube while the other end of thisseries circuit is connected to the high voltage supply for this vacuumtube plate.

The selection signal current must be applied to the concerned one of thethree elementary transfer circuits I, II, III, with a time lead withrespect to the application of the signal to be transferred to theterminals 10-11. This time lead may be taken of a value equal to theminimum duration of the condition of a portion of the incoming signal,such as stated above. In the example concerned, therefore, such a timelead of the selection control signal I, will be taken equal to 2.

Each time the three currents I I and I coexist during the transfer cycleT within one of the elementary transfer circuits, for instance incircuit I, the current i Fig. 2, passes through the load impedance ofthis circuit I. The two other circuits II and III, being unselected, donot transmit the incoming signal to their respective loads.

While the overall operative process is obvious, for cl'aritys sake theoperation of an elementary transfer circuit of the arrangement will beexplained in more detail. For such an explanation, it will be consideredthat the windings 3 and 4 each have n turns and the windings 5 and 6each have 11 /2 turns, whereas the windings 7 and 3 are constituted byIt turns of wire. These values do not present limitations for realizingthe invention, but are related, for the two pairs of windings 34 and5-6, to the characteristics of the magnetic material of the cores 1-2,and more definitely to the above selected ratios between the timeintervals of the different portions of the electric signal applied at10-11.

The hysteresis cycles shown in Fig. 3 are considered as substantiallyrectangular and correspond to hysteresis cycles within a magneticmaterial such as a ferrite. In order to simplify the explanation, cores1 and 2 will be considered to be without magnetic losses. Anyarrangement for compensating irregularities in these hysteresis cyclesand well-known per so, may be provided but such arrangements, beingquite outside of the field of the invention will not be shown ordescribed therein.

Without any current in any winding, the two magnetic cores in thiscircuit are both in the magnetic condition N, Fig. 2, with a remanentinduction Br., Fig. 3. For any signal I I which may be applied to theinput terminals 10-11, such a pair of cores will remain in thiscondition, thus blocking the transfer of said signal to their loadimpedance 9, provided no current circulates through their controlwindings 5-6. They merely act as short-circuits.

Considering a cycle of transfer wherein the first circuit I must beeffectively operating, the selection control current I is applied to theinput 13 before a time interval 0/2 preceding the beginning of the cycleT. The action of this current which, in the conditions of the windingsstated above, may have a value I for instance, is unidirectional, and iturges the magnetic conditions of both cores to be modified towards thecondition P, remanent induction +Br. Everything is then so as if the twomagnetic cores 1 and 2 were open-circuit connections when no I,,I signalexists. No current passes through the load impedance 9.

The ampere-turns in each core, due to the selection control current,are:

""I Jlo/Z In each core, and each time the current I for the core 1,

and the current T for the core 2, assumes the value I the followingampere-turns are developed:

At the beginning of the recording cycle, illustrated in Fig. 2., the Icurrent presents the value I and consequently ensures activation. Themagnetic field in core 1 becomes:

As the second core stays at the saturated condition P, in the loadcircuit 9, the impedance of which may be considered as a pure resistiveimpedance R, in order to simplify the relations the condition in loadcircuit 9 due to the flux through core 1 is such that:

n R.t,,

being the magnetic fiux through core 1.

The i current being constant, the flux charge within the core 1 andeffective upon output coil 7 is proportional to the elapsed timeinterval. If:

(vi) R.i /n=K during the time interval dt=At =6/2, the magnetic fluxvaries by:

and core 1 reaches N on the hysteresis cycle a in Fig. 3, the changefollows the path defined by the arrows shown. This magnetisation level Nis higher than the N level.

After this time interval 0/2, current 1,, is zero for a time interval 0,but on the other hand, the value of the current I which was zero,becomes I and the action of said latter current becomes effective uponcore 2.

The current 2",, which then passes from output coil 8 through the loadimpedance 9 maintains its value but is of opposite direction, orpolarity. The core 1 has a tendency to return to the saturated Pcondition; its flux change therefore, as effective through output coil 7upon load circuit 9 is equal and opposed to that defined above.Consequently said change is added to the effect of the change occurringin core 2 and effective through output coil 8 upon load circuit 9. Inthe load circuit 9, therefore, the condition is:

(viii) Ri l) i.e., the same as mentioned above under (vii), and after atime interval 0 the core 1 is brought back to its P condition,hysteresis cycle a; and the core 2 is brought to its N condition,hysteresis cycle b.

The values of the currents I and T then are reversed during a furthertime interval 0, with overall conditions corresponding to those above,and at the end of said time interval 9, the core 1 is brought to the Ncondition and the core 2, to the P condition.

From this point, and for a further time interval of 0/2, the I and Tcurrents again reverse. The same applies to the energizations of thecores 1 and 2. This time both cores are brought to the same magneticcondition, denoted by P on their respective hysteresis cycles.

Generally speaking, the paired cores of a transfer circuit will bebrought to the same magnetic condition (here P each time within atransfer cycle they are controlled for the same number of times by thehigher value of their respective activation currents I and I Theoperation will continue until the end of the transfer cycle concerned,in a way quite similar to that described for the first variations in theinput signal. The end of a transfer cycle is given by the cessation ofthe selection control current. The cores 1 and 2 both will be broughtback to their N conditions.

However it may occur that, at the instant when the selection controlcurrent is interrupted, the cores 1 and 2 are in different magneticconditions, for instance the first at P and the other one at N Therenewal of a recording process, viz. a transfer cycle process togetherwith a previously made selection, cannot be insured if there is nosuitable time interval available enabling both cores to return to theirN conditions. In order to reduce such a time interval and accelerate thereturn to N conditions of the cores, irrespective of their finalconditions, advantage is taken from the application, during a minimumtime interval of 0/ 2 in the given example, of both I and I currents attheir higher values, here considered as 1 Since the actions of suchcurrents are unidirectional, as stated above, they tend to bring bothcores to their N condition, and thereby accelerate the return of bothcores to said state.

In case such a return action were impossible, or the concomitantexistence of currents I and I at their respective higher values couldnot be obtained, another arrangement could be provided: in" the formof apair of auxiliary windings mounted upon the cores of each pair andreceiving, after each transfer cycle T of operation of the device, asuitable I current during an appropriate time interval 0/ 2; the windingdirection'of such windings is the same as that used for the activationwindings 3 and 4, and all such return control windings being seriallyconnected, if necessary, in a single channel throughout the wholedevice.

Naturally more than one activation Winding and more than one selectioncontrol winding may be mounted upon a core for any multiplex controlpurposes other than those required for a transfer and routing deviceaccording to the invention.

It may be noticed that, in the illustrative embodiment just described,the transfer of reversible energy is made Without discontinuitythroughout any transfer cycle T. As seen from the loads 9, the transfercircuits thus achieved appear to be equivalents of vacuum tube circuitsof the so-called Class-A amplifiers. It would be possible however toensure such a control that each transfer circuit be equivalent to aso-called Class-B amplifier, viz. in each period of the cycle one of thecores would be brought back to its saturated condition while the othercore would assume an intermediate condition; this would be the case ifthe time intervals were made equal either to 0/2 or 30/2 for the changesin the currents I and T It would even be possible to design one of thesetime intervals such that for each period within the transfer cycle, oneof the cores be brought to its N condition whereas the other one wouldbe brought to its P condition; in such a case, each transfer circuitwould appear, if seen from the load, as equivalent to a Class-C pushpullamplifier. Of course, in said latter control circuits, the transfer ofreversible energy would not be continuous.

Any technological changes in the given examples, such as apparent fromthe present state of the art, may be made without departing from thescope of the invention as defined by the appended claims.

Having now described and ascertained my invention, I claim:

1. In combination, a pair of magnetic cores of substantially identicalrectangular hysteresis cycles, at least an activation winding, atransfer control winding and a pickup winding on each of said cores, anoutput load serially connected between the pick-up windings of said pairof cores, means for simultaneously applying a transfer control currentto both said transfer control windings, and means for applying to one ofsaid activation windings an electric signal having a two-levelrectangular current wave-form and to the other one of said activationwindings and concomitantly therewith another electric signal of awave-form complementary with respect to the first.

2. A combination according to claim 1, wherein the winding directions ofsaid transfer control and activation windings are opposite and whereinthe pick-up winding on one core is oppositely wound from that on theother core in each pair.

3. A combination according to claim 1, wherein corresponding ends ofsaid pick-up windings are connected to the same potential referencepoint and said load is serially connected between the other ends of saidwindings.

4. A combination according to claim 1, wherein said transfer controlwindings are serially interconnected in additive relation, one end ofsaid connection being connected to a predetermined potential referencepoint and the other end being connected to a current input.

5. In a signal transfer system, a plurality of transfer circuits eachcontaining a pair of magnetic cores of substantially rectangularhysteresis characteristic, at least an activation winding, a transfercontrol winding and a pickup Winding on each of said cores, means forconnecting in series the activation windings of one of said cores ineach pair of cores, means for connecting in series the activationwindings of the other core in each of said pairs of cores, means forsimultaneously applying to said two series connections of activationwindings two series respectively of incoming signals in substantiallycomplementary wave forms, means for connecting in series the transfercontrol windings of each pair of cores, means for applying separatelyselection control signals to said series connections of transfer controlwindings, and separate load circuits connected to at least one of saidpickup windings of each pair of cores.

6. System according to claim 5, wherein the pickup windings of each pairof cores are serially connected, each of said series connections ofpickup windings including a load circuit connected between said pickupwindings.

7. System according to claim 5, wherein the activation windings and thetransfer control windings for each pair of cores have substantiallyopposite winding directions, and wherein the pickup windings for eachpair of cores have winding directions opposite to each other.

8. System according to claim 5, wherein the number of turns of eachtransfer control winding is half the number of turns of each activationwinding.

9. System according to claim 5, comprising a pair of vacuum tube plateterminals and direct power supply means connected, respectively, toopposite ends of the series connections of said activation windings.

10. System according to claim 5, comprising a number of vacuum tubeplate terminals connected to one end of said transfer control windings;there being provided direct current plate supply means connected to theother end of said transfer control windings.

11. System according to claim 5, comprising a number of vacuum tubeplate terminals connected respectively, to one end of said activationwindings and one end of said transfer control windings; there beingprovided direct current supply means connected to the other end of saidseries connections of said activation windings and to the other end ofsaid transfer control windings.

12. System according to claim 5, wherein said transfer control windingsare supplied with signals predeterminedly advanced with respect to saidincoming signals.

13. System according to claim 5, wherein said incoming signals includepulses of predetermined length and pulses of twice said length eachpulse being followed by a space of pulse length.

14. System according to claim 5, wherein said incoming signals includepulses of predetermined length and pulses of twice said length eachpulse being followed by a space of pulse length, and wherein saidtransfer control windings are supplied with signals advanced withrespect to said incoming signals by one pulse length.

15. System according to claim 5, wherein said incoming signals includepulses of predetermined length and pulses of twice said length eachpulse being followed by a space of pulse length, and transfer controlwindings are supplied with signals advanced with respect to saidincoming signals by one pulse length, and wherein the number of turns ofeach transfer control winding is half the number of turns of each ofturns of each activation winding.

16. In a signal transfer system, a plurality of elementary magnetictransfer circuits each comprising a number of cores having substantiallyidentical rectangular hysteresis characteristics and each comprisingseparate activation means for said cores, transfer control means andpickup means, means for connecting the activation means of the differentcircuits in series forming several separate series connections, meansfor applying substantially complementary input signals to said seriesconnections of activation means, means for applying input signals tosaid transfer control means predeterminedly advanced with respect tosaid activation input signals, and separate load circuits connected tosaid pickup means.

17. System according to claim 16, wherein said activation and transfercontrol means in each transfer circuit include a pair of windings ofopposite winding direction, corresponding activation windings of thedifferent transfer circuits being serially interconnected; and whereineach of said pickup means includes a pair of windings of windingdirections opposite to each other and a load circuit connected betweensaid pickup windings.

18. System according to claim 17, wherein said transfer control meanshas windings of half the number of turns of the windings of saidactivation means, and wherein the input signals include pulses of onepredetermined length, and pulses of twice said length each pulse beingfollowed by a space of pulse length; the transfer control signals beingapplied advanced with respect to the activation signals by saidpredetermined pulse length of said activation signals.

19. In a magnetic circuit system, an array of groups of magneticcircuits, each circuit including a core structure having a substantiallyrectangular hysteresis characteristic and having at least an activationwinding, a transfer control winding and a pickup winding; means forconnecting in series a first activation winding in each of said circuitgroups, means for connecting a second activation winding in each of saidcircuit groups, and connecting said second activation windings inseries, means for applying to said serially connected activationwindings input signals in opposite phase relationship, and means forapplying separate selection control signals to at least one transfercontrol winding in circuit with said activation windings, and a loadcoupled to at least one pickup winding in circuit with said activationand transfer control windings.

References Cited in the file of this patent UNITED STATES PATENTS2,021,099 Fitz Gerald Nov. 12, 1935 2,666,151 Rajchman Jan. 12, 19542,717,965 Ramey Sept. 13, 1955 2,719,773 Karnaugh Oct. 4, 1955 2,719,961Karnaugh Oct. 4, 1955 2,779,934 Minnick Jan. 29, 1957 2,831,150 Wrightet al Apr. 15, 1958 OTHER REFERENCES Electronics, Apr. 1953, pp.146-149.

